The Early Universe

The Big Bang
1) The Big Bang - The Universe began in an initial state of very high temperature and density.
2) Cast of Characters - The early Universe was composed of a simple list of particles and antiparticles.
3) Equilibrium & Decoupling - Radiation dominated the early Universe because radiation and matter were in thermal equilibrium.
4) The First Three Minutes - The present abundances of helium and deuterium in the Universe were produced in the first three minutes.
5) Subsequent Evolution - The combination of protons and electrons into hydrogen atoms decoupled radiation and matter.
6) Triumph of the Big Bang - The Steady State Model of the Universe was rejected after discovery of the CBR.

The CBR
1) Discovery - The CBR was discovered by accident in 1965 by Arno Penzias and Robert Wilson.
2) Spectrum and Temperature - The blackbody curve of a body at 2.7 K is identical to the COBE CBR data. 
3) Motion Relative to CBR - The CBR's dipole anisotropy reveals that Earth moves at 600 km/sec relative to the CBR.
4) Isotropy and Anisotropy - The isotropy of the CBR indicates the early Universe was very uniform.
5) Fluctuations - The COBE data show small fluctuations in the background radiation.
6) Constraints on Cosmology - Detailed study of the CBR implies severe constraints on the thermal history of the Universe.

Inflationary Universe
1) Problems with Hot Big Bang - The horizon problem and the flatness problem may be solved with better theories of elementary particles.
2) Unification of the Forces - The four forces of nature are very different now but acted as one force in the very early Universe.
3) Vacuum Energy - A non-zero cosmological constant may have caused the very early Universe to inflate exponentially.
4) Inflationary Expansion - The vacuum energy density can cause the Universe to grow by a factor of 10^50 in the first fraction of a second.
5) Solution of the Problems - An early inflationary era could explain all the problems presented by the standard big bang.
6) Fluctuations and Structure - The theory of inflation also predicts small density fluctuations would have occurred in the early Universe. 

Formation of Structure
1) Structure from Uniformity - Galaxies formed within one billion years after the big bang.
2) Top Down Theories - Superclusters form first and then fragment to form smaller structures.
3) Bottom Up Theories - Globular clusters of stars form first and then assemble into galaxies and larger structures.
4) Role of Dark Matter - Dark matter can begin to clump together earlier than normal matter.
5) Simulations of Structure Growth - Computer calculations are able to simulate and reproduce the large scale structure of the Universe.
6) Where it Stands - The identity and role of the dark matter of the Universe is a question not yet fully answered.

The Planck Era
1) The Planck Scale - The very early Universe requires a quantum mechanical theory of gravity.
2) Quantum Gravitation - A consistent theory of quantum gravitation has not yet been discovered.
3) Spacetime Foam - On the Planck scale space and time become a discontinuous bubbling foam.
4) Breakdown of Current Laws? - For the small Planck scale of the earliest Universe, current laws of physics break down and cannot be applied.